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Evolution re-run test to probe life’s predictability

A 500-million-year-old bacterial gene got a second chance at evolution this year. The experiment may help biologists understand the extent to which evolution is predictable.

Biologists have long wondered whether life would evolve the same way again if we could rewind the tape. Eric Gaucher and Betül Arslan at Georgia Tech University in Atlanta hope to find out.

They focused on EF-Tu, a gene in Escherichia coli that plays a crucial role in protein synthesis. Gaucher had previously worked out what this gene’s DNA sequence must have been 500 million years ago, by comparing the sequences of many modern bacteria and reasoning backwards.

Now Arslan has synthesised the ancient gene and inserted it into E. coli in place of the modern version. The bacteria with the old gene grew less than half as fast as usual. Arslan then let eight bacterial lines evolve independently for 1000 generations.

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All eight lineages eventually grew faster – a sign that evolution had occurred. When Arslan sequenced their genomes, though, she found that EF-Tu was unchanged. What had evolved – differently in each lineage – were the genes that interact with EF-Tu. She reported the work at NASA’s Astrobiology Science Conference 2012 in Atlanta.

The sheer number of interacting genes in protein synthesis means that random mutations are more likely to hit one of EF-Tu’s partners than EF-Tu itself. Eventually, though, EF-Tu may begin to evolve – either following the same path it began 500 million years ago or not. The experiment continues.